Separation of organic compounds



Patented Oct. 2, 1945 r 2,885,981 SEPARATION or ORGANIC COMPOUNDSBernard S. Friedman, Riverside, 111., asslgnor to Universal Oil ProductsCompany, Chicago, 111., a corporation of Delaware No Drawing.

12 Claims.

This invention relates to the separation of organic compounds havingdifferent degrees of saturation and more particularly to a novel solventtherefor and to a process using the same.

The invention-is particularly applicable to the treatment of hydrocarbonfractions which, as usually recovered from various sources, containsaturated and unsaturated hydrocarbons. For example, normally liquidproducts of a cracking process contain oleflns, aromatics, paraflins andnaphthenes. Likewise, the products recovered by distillation of crudeoil contain parafflns, naphthenes, aromatics and, in most cases. a smallamount of oleflns. Likewise, normally gaseous products of a crackingprocess contain oleflnic gases such as propylene and butylenes, andparaflinic gases such as propane and butanes.

In many cases, it is desirable to separate the unsaturated from thesaturated hydrocarbons, but this cannot be accomplished by purelyfractional distillation means in practical operations because of thesimilarity in boiling points of the various hydrocarbons.

Other organic compounds are recovered from various sources includingsynthetic processes, wherein the products contain organic compounds ofdiflerent degrees of saturation. For example, saturated and unsaturatedglycerides are frequently recovered in admixture, and their separationcannot be effected by purely fractional distillation means-in practicaloperations.

In a broad aspect the present invention relates to a process forseparating a mixture of organic compounds of difiering degrees ofsaturation, which comprises treating said mixture with a solventcomprising an aliphatic sulfonamide.

In another aspect the present invention relates Application November 29,1943, Serial No. 512,238

to the separation of a mixture of hydrocarbons I having difieringdegrees of saturation and similar boiling points, which comprisestreating said mixture with a solvent comprising an aliphatic sulbons isintended to include the paraflins and/or naphthenes, while the termunsaturated hydrocarbonsis intended to include the oleflns and/oraromatics. The olefins include both the mono and poly-olefinichydrocarbons.

Thus, the invention may be utilized for the separation of olefins and/oraromatics from parafiins and/or naphthenes. Likewise, the invention maybe utilized forthe separation of, monoolefins from di-olefins.

The present invention is characterized by a novel solvent whichcomprises an aliphatic monoor poly-sulfonamide, and more particularly analiphatic monoor di-sulionamide.

In accordance with the invention, thealiphatic portion of the solventpreferably contains from 1 to about 6 carbon atoms per atom of sulphur.Particularly preferred solvents comprise propane mono-sulfonamide(CaHvSOzNHz) and butane mono-sulfonamide (C4H9S02NH2) The aliphaticgroup may be straight chain or branched chain structure or mixturesthereof, such as certain eutectic mixtures which a number of these mixedcompounds form.

It is also within the scope of the invention to include derivatives ofthe aliphatic sulfonamides. Examples of such derivatives may comprisecompounds in which one or more of the hydrogen atoms attached to thealiphatic group is replaced by a hydroxy group, a halogen group,an aminogroup, or the like. 7

It is to be noted that a number of different compounds may besatisfactorily employed in the process of the present invention, but itisunderstood that these various alternative compounds are notnecessarily equivalent in their effectiveness. The choice as topreferred solvent to be employed in any given operation will depend uponthe characteristics of the charging stock and the type of separation tobe efiected.

In cases where the unsaturate'content of the mixture is high, it may benecessary to dilute the solvent with water, alcohol, glycol, etc. Forexample, it has been found that butane sulfonamide is mutually misciblewith a normal heptane-benzene mixture having a benzene content of about84%. The amount of water, alcohol, glycol or the like to be added shouldbe suflicient so that a separation of an extract phase and a raflinatephase occurs. For example, in the case of the butane sulfonamide and 84%benzene mixture heretofore set forth, a satisfactory solvent wasprepared containing 91% by volume of butane sulfonamide and 9% by volumeof water.

The solvents of the present invention may in fonamide and 9% by volumeof water.

many cases be obtainable in the open market or,

.if a particular solvent is not so obtainable, it may be readilysynthesized by well-known means.

Thus, for example, butane sulfonamide may be prepared by reacting butanewith a mixture of sulphur dioxide" and chlorine in the presence of lightto produce butane sulfonyl chloride, and the butane sulfonyl chloridemay then be reacted with ammonia to produce the butane sulfonamide.

' The operation of the solvent extraction process is relatively simpleand may. comprise introducing the hydrocarbon mixture to be extractedinto a suitable extraction zone. The extraction zone may or may notcontain baiiie plates, bubble decks, side to side pans, or othersuitable packing. The extraction zone may be equipped with stirring orother contacting means in order to obtain emcient contacting of thehydrocarbons and solvent. The solvent extraction is effected underconditions of temperature and pressure in order to form an extract phasecontaining a major portion of the solvent and a major portion of theunsaturated hydrocarbons, and a raffinate phase containing a majorportion of the saturated hydrocarbons.

The temperature employed is preferably atmospheric or slightlysuperatmospheric but it should be high enough to maintain the solvent inliquid phase in caseit is solid at ordinary temperatures, but must bebelow that at which decomposition of the solvent or hydrocarbons occurs.The pressure to be employed is usually atmospheric or moderatelysuperatmospheric but likewise should be sufllcient in order to maintainthe hydrocarbons and solvent in liquid phase. When treating normallygaseous hydrocarbons, a higher superatmospheric pressure is employed inorder to maintain the hydrocarbons in substantially liquid phase.

Usually more than one extraction is required in order to effectsubstantially complete separation of the unsaturated from the saturatedhydrocarbons. In some cases, however, one extraction may be sufllcientwhen it is required to lower only slightly the concentration of theunsaturated hydrocarbons in the mixture or in case the charging stockoriginally contains only a small percentage of unsaturated hydrocarbons.

After formation of the extract and rafflnate phases, the solvent may beseparated from the hydrocarbons by various means including: (1)distillation at increased temperature and/ or reduced pressure; (2)adding water or the like in order to decrease the solubility of thehydrocarbons in the solvent and (3) counter-extracting the hydrocarbonsfrom the solvent by contacting the extract phase with a secondarysolvent which is immiscible with the first solvent and may comprise, forexample, a parafiinic or naphthenic hydrocarbon of higher or lowerboiling point than the solute. The second solvent is then separated fromthe solute by ordinary fractional distillation means.

The following examples are introduced for the purpose of furtherillustrating the novelty and utility of the present invention but notwith the intention of unduly limiting the same.

In the following "examples the solvent com prised a mixture of 91% byvolume of butane sul- The experiments were all conducted at roomtemperature and atmospheric pressure. These experiments were batch testsin which the hydrocarbon mixture and the solvent were stirred in amixing zone and thereafter allowed to settle in order to separate anextract phase and a raflinate phase.

. The results shown in the following examples are based upon a singleextraction. It is understood that further separation is obtainable bythe use of additional extraction stages.

E'zample I to 14% in the rafllnate in one extraction. By additionalextractions the benzene content of the ramnate may be reduced to aloweramount.

Example I! In this example the charging stock contained 28.5% by volumeof benzene and 71.5% by volume of normal heptane. It was likewisetreated with an equal volume of the butane sulfonamidewater solvent. Thehydrocarbons in the extract phase comprised 76.5% by volume of benzene.while the hydrocarbons in the rafllnate phase comprised 22% by volume ofbenzene. Thus the volume of benzene in the charge was reduced in oneextraction from 28.5% to 22% in the ramnate.

Example III The charging stock in this example contained 49% by volumeof benzene and 51% by volume of normal heptane. It was likewise treatedwith an equal volume of the butane sulfonamide-water solvent. Thehydrocarbons in the extract phase comprised 83% by volume of benzene andthe hydrocarbons in the rafllnate phase comprised 40.5% by volume ofbenzene. Here, one extraction reduced the volume of benzene from 49% inthe charge to 40.5% in the rafiinate.

I claim as my invention:

1. A process for separating a mixture of organic compounds of differentdegrees of saturation which comprises treating said mixture underconditions to form an extract phase and a railinate phase with a solventcomprising an alkyl sulfonamide containing the NHz group.

2. In a solvent extraction process for separating a, mixture ofhydrocarbons into fractions of difiering degrees of saturation withrespect to carbon-hydrogen ratio, the step of extracting saidhydrocarbons with an alkyl sulfonamide containing the NHz group underconditions to form an extract phase and a rafflnate phase.

3. A process for separating a mixture of hydrocarbons of differingdegrees of saturation which comprises treating said mixture underconditions to form an extract phase and a rafflnate phase with aselective solvent comprising an alkyl sulfonamide containing the NH:group .and in which the alkyl group contains from 1 to about 6 carbonatoms per atom of sulphur.

4. A process for separating a mixture of hydrocarbons of differingdegrees of saturation which comprises treating said mixture underconditions to form an extract phase and a rafilnate phase with aselective solvent comprising an alkyl mono-sulfonamide in which thealkyl group contains from 1 to about 6 carbon atoms.

5. A process for separating a mixture of hydrocarbons of difieringdegrees of saturation which comprises treating said mixture underconditions to form an extract phase and a raflinate phase with aselective solvent comprising an alkyl di-sulfonamide in which the alkylgroup contains from 1 to about 6 carbon atoms per atom of sulphur.

6. A process for separating unsaturated hydrocarbons from saturatedhydrocarbons which comprises treating a mixture of unsaturated andsaturated hydrocarbons under conditions to form an extract phase and araflinate phase with a selective solvent comprising an alkylmono-sulfonamide in which the alkyl group contains from 1 to about 6carbon atoms.

7. The process of claim 6 further characterized in that said unsaturatedhydrocarbons comprise olefins and aromatics.

8,. The process of claim 6 further characterized in that saidunsaturated hydrocarbons comprise olefins.

9. The process of claim 6 further characterized in that said unsaturatedhydrocarbons comprise aromatics.

10. A process for separating an aromatic hydrocarbon from a mixturethereof with a saturated hydrocarbon which comprises treating themixture with butane sultonamide under conditions to form an extractphase and a rafllnate phase.

11. A process for separating an aromatic hydrocarbon from a mixturethereof with a saturated hydrocarbon which comprises treating themixture with a butane sulfonamide-water solvent under conditions to forman extract phase and a rafiinate phase.

12. A process for separating an aromatic hydrocarbon from a mixturethereof with a saturated hydrocarbon which comprises treating themixture with propane sulfonamide under conditions to form an extractphase and a raflinate phase.

BERNARD S.

